Behavioral simulation is a high level simulation of the architecture of a digital system. Behavioral simulation is performed using a behavioral description of digital system, e.g., a circuit design, that exists at an early stage of a design flow. One example of a behavioral description is a circuit design expressed programmatically as a register transfer level (RTL) description. The RTL description describes the behavior of the digital system as data transfers that occur between registers each clock cycle. Hardware description languages such as VHDL and Verilog can be used to specify RTL descriptions.
In some cases, portions of the circuit design expressed in RTL are pin dependent. The pin dependent portions may have default pin configurations. These pin configurations often change during one or more stages of a design flow through which the behavioral description of the circuit design is processed.